One of the best resources I have seen for small businesses on this topic is the Content Marketing ROI Guide (requires paid registration) over at Smart Insights. I recommend it regularly to small businesses wanting to get to grips with measurement and ROI models.
We have added to this site a new section; a curation of the best Content Marketing ROI related stories that we have found from around the web. Feel free to comment below on this post to suggest more.
In order to ensure traffic goes to every author, we will write a quick overview and link you through to the source. And we encourage you to click through. There are some fantastic writers from a blend of backgrounds charted and recording what they are doing in this space, and we intend to highlight those that pique our interest.
So, feel free to have a browse here.